10Gtek 40G QSFP+ DAC Cable - 40GBASE-CR4 Passive Direct Attach Copper Twinax QSFP Cable for Juniper EX-QSFP-40GE-DAC-50CM Devices, 0.5-meter(1.64ft)

Good Price, Worked well with my Infiniband + GBe Card

Set up two switch stack with 4 Juniper EX4300s in each stack. I used the . 5 meter for the links between the individual switches and a 1 meter for the link between sw0 and sw3. -- hth

Works as advertised (@ 40G) with a Mellanox ConnectX-3 and a Mellanox IS5022 unmanaged IB switch.

I purchased several of these DAC cables (2 m length) to connect my infrastructure, including several servers and firewalls with Intel X520 NICs, Mellanox SX6036 switches and Aruba 2930F switches. Unfortunately, I ran into compatibility issues across ALL devices. On Intel X520 NICs (82599ES chipset), the link would flap every few seconds. Logs on my servers clearly showed frequent link-up and link-down events. After deeper investigation, it became evident that the cable is a passive DAC without proper equalization. The ixgbe driver rejects it intermittently due to the lack of proper SFP EEPROM data. Additionally, my aruba switch (tested on multiple ports and firmware versions) refused to establish a link altogether with this module. The Mellanox SX6036 was more forgiving, but even there, the link proved unstable. While the build quality appears solid, this DAC lacks the proper signaling and compatibility required for more professional hardware. It might work in less strict environments, but I would not recommend it for gear that expects compliant SFP+ modules. 📌 Note: This is a passive, unequalized DAC, which makes it more prone to signal integrity issues over longer distances or with professional hardware. ✔️ Summary: Probably fine in some lab setups, but not a reliable option for enterprise-class hardware. I’d recommend using Intel-compatible or active DACs for those environments. Update: 10GTek (the seller) proactively contacted me about my experience. They offered solutions up to a full return. They even provided deep technical engineering support regarding reprogramming the modules to fit my needs. I’ll never buy somewhere else. Superior support!!

Good quality, works as advertised with Juniper EX4300 40Gbe ports